Returns from an OpcodeCall, popping a number of scope depths off the stack as it does so. It evals the topmost thing on the stack. to remove any local variable references and replace them with their current values, and then performs the equivalent of a popscope, then jumps back to where the routine was called from. It also checks to ensure that the argument stack contains the arg bottom marker. If it does not, that proves the number of parameters consumed did not match the number of arguments passed and it throws an exception (to avoid stack misalignment that would happen if it tried to continue).